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Derek Jones8917af72010-03-05 12:41:45 -0600[diff] [blame]31<td><h1>CodeIgniter User Guide Version 2.0.0</h1></td>
Derek Allard2067d1a2008-11-13 22:59:24 +0000[diff] [blame]32<td id="breadcrumb_right"><a href="../toc.html">Table of Contents Page</a></td>
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43<a href="http://codeigniter.com/">CodeIgniter Home</a> &nbsp;&#8250;&nbsp;
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45Creating Libraries
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57
58<h1>Creating Libraries</h1>
59
60<p>When we use the term "Libraries" we are normally referring to the classes that are located in the <kbd>libraries</kbd>
61directory and described in the Class Reference of this user guide. In this case, however, we will instead describe how you can create
62your own libraries within your <dfn>application/libraries</dfn> directory in order to maintain separation between your local resources
63and the global framework resources.</p>
64
65<p>As an added bonus, CodeIgniter permits your libraries to <kbd>extend</kbd> native classes if you simply need to add some functionality
66to an existing library. Or you can even replace native libraries just by placing identically named versions in your <dfn>application/libraries</dfn> folder.</p>
67
68<p>In summary:</p>
69
70<ul>
71<li>You can create entirely new libraries.</li>
72<li>You can extend native libraries.</li>
73<li>You can replace native libraries.</li>
74</ul>
75
76<p>The page below explains these three concepts in detail.</p>
77
78<p class="important"><strong>Note:</strong> The Database classes can not be extended or replaced with your own classes,
79nor can the Loader class in PHP 4. All other classes are able to be replaced/extended.</p>
80
81
82<h2>Storage</h2>
83
84<p>Your library classes should be placed within your <dfn>application/libraries</dfn> folder, as this is where CodeIgniter will look for them when
85they are initialized.</p>
86
87
88<h2>Naming Conventions</h2>
89
90<ul>
91<li>File names must be capitalized. For example:&nbsp; <dfn>Myclass.php</dfn></li>
92<li>Class declarations must be capitalized. For example:&nbsp; <kbd>class Myclass</kbd></li>
93<li>Class names and file names must match.</li>
94</ul>
95
96
97<h2>The Class File</h2>
98
99<p>Classes should have this basic prototype (Note: We are using the name <kbd>Someclass</kbd> purely as an example):</p>
100
101<code>&lt;?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
102<br /><br />
103class Someclass {<br />
104<br />
105&nbsp;&nbsp;&nbsp;&nbsp;function some_function()<br />
106&nbsp;&nbsp;&nbsp;&nbsp;{<br />
107&nbsp;&nbsp;&nbsp;&nbsp;}<br />
108}<br /><br />
109?&gt;</code>
110
111
112<h2>Using Your Class</h2>
113
114<p>From within any of your <a href="controllers.html">Controller</a> functions you can initialize your class using the standard:</p>
115
116<code>$this->load->library('<kbd>someclass</kbd>');</code>
117
118<p>Where <em>someclass</em> is the file name, without the ".php" file extension. You can submit the file name capitalized or lower case.
119CodeIgniter doesn't care.</p>
120
121<p>Once loaded you can access your class using the <kbd>lower case</kbd> version:</p>
122
123<code>$this-><kbd>someclass</kbd>->some_function();&nbsp; // Object instances will always be lower case
124</code>
125
126
127
128<h2>Passing Parameters When Initializing Your Class</h2>
129
Derek Allard652612d2009-07-30 06:32:31 +0000[diff] [blame]130<p>In the library loading function you can dynamically pass data as an array via the second parameter and it will be passed to your class
Derek Allard2067d1a2008-11-13 22:59:24 +0000[diff] [blame]131constructor:</p>
132
133<code>
134$params = array('type' => 'large', 'color' => 'red');<br />
135<br />
136$this->load->library('Someclass', <kbd>$params</kbd>);</code>
137
138<p>If you use this feature you must set up your class constructor to expect data:</p>
139
140<code>&lt;?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');<br />
141<br />
142class Someclass {<br />
143<br />
144&nbsp;&nbsp;&nbsp;&nbsp;function Someclass($params)<br />
145&nbsp;&nbsp;&nbsp;&nbsp;{<br />
146&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;// Do something with $params<br />
147&nbsp;&nbsp;&nbsp;&nbsp;}<br />
148}<br /><br />
149?&gt;</code>
150
151<p class="important">You can also pass parameters stored in a config file. Simply create a config file named identically to the class <kbd>file name</kbd>
152and store it in your <dfn>application/config/</dfn> folder. Note that if you dynamically pass parameters as described above,
153the config file option will not be available.</p>
154
155
156
157
158
159
160
161<h2>Utilizing CodeIgniter Resources within Your Library</h2>
162
163
164<p>To access CodeIgniter's native resources within your library use the <kbd>get_instance()</kbd> function.
165This function returns the CodeIgniter super object.</p>
166
167<p>Normally from within your controller functions you will call any of the available CodeIgniter functions using the <kbd>$this</kbd> construct:</p>
168
169<code>
170<strong>$this</strong>->load->helper('url');<br />
171<strong>$this</strong>->load->library('session');<br />
172<strong>$this</strong>->config->item('base_url');<br />
173etc.
174</code>
175
176<p><kbd>$this</kbd>, however, only works directly within your controllers, your models, or your views.
177If you would like to use CodeIgniter's classes from within your own custom classes you can do so as follows:</p>
178
179
180<p>First, assign the CodeIgniter object to a variable:</p>
181
182<code>$CI =&amp; get_instance();</code>
183
184<p>Once you've assigned the object to a variable, you'll use that variable <em>instead</em> of <kbd>$this</kbd>:</p>
185
186<code>
187$CI =&amp; get_instance();<br />
188<br />
189$CI->load->helper('url');<br />
190$CI->load->library('session');<br />
191$CI->config->item('base_url');<br />
192etc.
193</code>
194
195<p class="important"><strong>Note:</strong> You'll notice that the above get_instance() function is being passed by reference:
196<br /><br />
197<var>$CI =&amp; get_instance();</var>
198<br />
199<br />
200<kbd>This is very important.</kbd> Assigning by reference allows you to use the original CodeIgniter object rather than creating a copy of it.
201<br /><br />
202<kbd>Also, please note:</kbd> If you are running PHP 4 it's usually best to avoid calling <dfn>get_instance()</dfn>
203from within your class constructors. PHP 4 has trouble referencing the CI super object within application constructors
204since objects do not exist until the class is fully instantiated.</p>
205
206
207<h2>Replacing Native Libraries with Your Versions</h2>
208
209<p>Simply by naming your class files identically to a native library will cause CodeIgniter to use it instead of the native one. To use this
210feature you must name the file and the class declaration exactly the same as the native library. For example, to replace the native <kbd>Email</kbd> library
211you'll create a file named <dfn>application/libraries/Email.php</dfn>, and declare your class with:</p>
212
213<code>
214class CI_Email {<br /><br />
215
216}</code>
217
218<p>Note that most native classes are prefixed with <kbd>CI_</kbd>.</p>
219
220<p>To load your library you'll see the standard loading function:</p>
221
222<code>$this->load->library('<kbd>email</kbd>');</code>
223
224<p class="important"><strong>Note:</strong> At this time the Database classes can not be replaced with your own versions.</p>
225
226
227<h2>Extending Native Libraries</h2>
228
229<p>If all you need to do is add some functionality to an existing library - perhaps add a function or two - then
230it's overkill to replace the entire library with your version. In this case it's better to simply extend the class.
231Extending a class is nearly identical to replacing a class with a couple exceptions:</p>
232
233<ul>
234<li>The class declaration must extend the parent class.</li>
235<li>Your new class name and filename must be prefixed with <kbd>MY_</kbd> (this item is configurable. See below.).</li>
236</ul>
237
238<p>For example, to extend the native <kbd>Email</kbd> class you'll create a file named <dfn>application/libraries/</dfn><kbd>MY_Email.php</kbd>, and declare your class with:</p>
239
240<code>
241class MY_Email extends CI_Email {<br /><br />
242
243}</code>
244
245<p>Note: If you need to use a constructor in your class make sure you extend the parent constructor:</p>
246
247
248<code>
249class MY_Email extends CI_Email {<br />
250<br />
251&nbsp;&nbsp;&nbsp;&nbsp;function My_Email()<br />
252&nbsp;&nbsp;&nbsp;&nbsp;{<br />
253&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;parent::CI_Email();<br />
254&nbsp;&nbsp;&nbsp;&nbsp;}<br />
255}</code>
256
257
258<h3>Loading Your Sub-class</h3>
259
260<p>To load your sub-class you'll use the standard syntax normally used. DO NOT include your prefix. For example,
261to load the example above, which extends the Email class, you will use:</p>
262
263<code>$this->load->library('<kbd>email</kbd>');</code>
264
265<p>Once loaded you will use the class variable as you normally would for the class you are extending. In the case of
266the email class all calls will use:</p>
267
268
269<code>$this-><kbd>email</kbd>->some_function();</code>
270
271
272<h3>Setting Your Own Prefix</h3>
273
274<p>To set your own sub-class prefix, open your <dfn>application/config/config.php</dfn> file and look for this item:</p>
275
276<code>$config['subclass_prefix'] = 'MY_';</code>
277
278<p>Please note that all native CodeIgniter libraries are prefixed with <kbd>CI_</kbd> so DO NOT use that as your prefix.</p>
279
280
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